Photometric variability of the Herbig Ae star HD 37806

Abstract

The more massive counterparts of T Tauri stars, Herbig Ae/Be stars, are known to vary in a complex way with no variability mechanism clearly identified. We attempt to characterize the optical variability of HD~37806 (MWC 120) on time scales ranging between minutes and several years. A continuous, one-minute resolution, 21 day-long sequence of MOST (Microvariability & Oscillations of STars) satellite observations has been analyzed using wavelet, scalegram and dispersion analysis tools. The MOST data have been augmented by sparse observations over 9 seasons from ASAS (All Sky Automated Survey), by previously non-analyzed ESO (European Southern Observatory) data partly covering 3 seasons and by archival measurements dating back half a century ago. Mutually superimposed flares or accretion instabilities grow in size from about 0.0003 of the mean flux on a time scale of minutes to a peak-to-peak range of <~0.05 on a time scale of a few years. The resulting variability has properties of stochastic "red" noise, whose self-similar characteristics are very similar to those observed in cataclysmic binary stars, but with much longer characteristic time scales of hours to days (rather than minutes) and with amplitudes which appear to cease growing in size on time scales of tens of years. In addition to chaotic brightness variations combined with stochastic noise, the MOST data show a weakly defined cyclic signal with a period of about 1.5 days, which may correspond to the rotation of the star.

Accepted for publication by Astron. & Astroph. 8 pages, 9 figures. For some reason Fig.5 incorrectly shows in arXiv: Contours OK, gray scale not

References in corpus (6)

• Magnetospheric accretion-ejection processes in the classical T Tauri star AA
• Photometric variability of the T Tauri star TW Hya on time scales of hours to years
• Main-Seqence Fitting Distance to the sigma Ori Cluster
• On the difference between Herbig Ae and Herbig Be stars
• Spectropolarimetric Observations of Herbig Ae/Be Stars. II. Comparison of Spectropolarimetric Surveys: HAeBe, Be and Other Emission-Line Stars
• MOST photometry of the enigmatic PMS pulsator HD 142666

Cited by in corpus (10)

• CSI 2264: Simultaneous optical and infrared light curves of young disk-bearing stars in NGC 2264 with CoRoT and Spitzer-- evidence for multiple origins of variability
• Rotationally modulated variations and the mean longitudinal magnetic field of the Herbig Ae star HD 101412
• Characterising the i-band variability of YSOs over six orders of magnitude in timescale
• Precise High-Cadence Time Series of Five Variable Young Stars in Auriga with MOST
• Variability at the Edge: Optical Near/IR Rapid Cadence Monitoring of Newly Outbursting FU Orionis Object HBC 722
• Stable and unstable accretion in the classical T Tauri stars IM Lup and RU Lup as observed by MOST
• A stable quasi-periodic 4.18 d oscillation and mysterious occultations in the 2011 MOST light curve of TWHya
• A multi-epoch, multi-wavelength study of the classical FUor V1515 Cyg approaching quiescence
• Characterising the magnetic fields of the Herbig Ae/Be stars HD97048, HD150193, HD176386, and MWC480
• V899 Mon: a peculiar eruptive young star close to the end of its outburst